(1) Technical Field
The present invention relates to techniques for signal processing. More specifically, the present invention relates to the performance of linear signal processing operations on data stored in a transformed (e.g. compressed) state without the need to transform the data out of the transformed state.
(2) Discussion
Data filtering or mapping techniques have been used for many years in the field of signal processing. Filters are used in a wide variety of applications, such as image processing, pattern recognition, noise reduction, data manipulation, data compression, and data encryption. Many of these filters can be used in conjunction with one another, e.g., for performing multiple functions such as pattern recognition and encryption at the same time.
In file compression, previously a signal had to be brought out of the transform (i.e., compressed) domain and reconstructed prior to any linear signal processing operation. To date, there has been no universal technique for performing linear filtering operations directly on a data in a transform domain (e.g. a multiresolution subband decomposition) without first inverse-transforming the data. Thus, signals or data on which an operation is to be performed must first be reconstructed prior to performing a linear filtering operation.
It is therefore desirable to provide a mechanism by which transformed data may be manipulated without the need for inverse-transforming the data first. Such a system would allow for a variety of linear operations to be performed on transformed data such as compressed images and data, as well as for searching through large databases of compressed data without the need for computationally expensive decompression and recompression.